Oriented sheath core type filament

ABSTRACT

The object of this invention is to make possible the manufacturing of sheath-core type super microfilaments from sheath-core type filaments such as hollow filaments, optical filaments and conjugate filaments continuously and stably by a simple and convenient means without requiring any apparatus of high-accuracy and high-level, characterized in that original filaments delivered from sheath-core type filament supply means are heated by infrared beams and the heated sheath-core type filaments are drawn at 100 times or more by a tension provided by the own weight or under a tension of 1 MPa or less.

1. FIELD OF THE INVENTION

This invention concerns a method of and an apparatus for manufacturingdrawn sheath-core type filaments and it especially relates tosheath-core type super microfilaments such as hollow supermicrofilaments, optical super microfilaments, conjugate supermicrofilaments drawn at a high draw ratio of 100 times or more andobtained by the simple and convenient drawing method.

2. BACKGROUND OF THE INVENTION

Super microfilaments have been used in various applications such asartificial leathers, wiping cloths and filters. However, since specialand complicated spinning methods such as island-in-sea type fiberspinning (for example, Japanese Patent Laid-Open No. Hei 7-258940) orspinning by dividual fibers (for example, Japanese Patent Laid-Open2002-220740) have been used, for the production of highly molecularoriented super microfilaments and having high quality with the fiberdiameter of 5 μm or less, they are expensive and cannot be drawn simplyand conveniently by using general purpose fibers.

As a method of drawing to obtain fibers with high tensile strength andhigh tensile modulus, the present inventors, et al. have proposed a zonedrawing method (Japanese Patent Publication No. Sho 60-24852), butfurther requirements are desirable for stable production of finefilaments by the zone drawing.

And, the request to produce super micro fibers in the field of fibersare extended to fibers having higher function and performance. However,it is difficult to produce at stable operation as the apparatus is morecomplicated and precise so that is expensive by the conventional methodto obtain super micro fibers. And the manufacturing methods of theconventional super micro fibers are not match the production of highperformance fibers as their production is high-mix low-volume productionthat it has been required the manufacturing means of high performancefibers of high quality in more simple and convenient ways. Therefore,the simple and convenient method is required also in sheath-core typesuper microfilaments which are the typical example of high performancefibers.

On the other hand, this invention concerns drawing technology offilaments by infrared rays heating but the technology regarding thesehas been performed in many ways conventionally (for example, JapanesePatent Laid-Open 2003-166115, pamphlet of International Laid-Open No.00/73556, Akihiro Suzuki, et al. “Journal of Applied Polymer Science”,Vol. 83, 1711-1716, 2002, Akihiro Suzuki and one other, PreliminaryAbstracts of Polymer Science Society, Japan, May 7, 2001, Vol. 50, No.4, pp. 787, Akihiro Suzuki and one other, “Journal of Applied PolymerScience”, Vol. 88, pp. 3279-3283, 2003, Akihiro Suzuki and one other,“Journal of Applied Polymer Science”, Vol. 90, pp. 1955-1958, 2003).Improving these technologies further, this invention is made effectivelyapplicable to the sheath-core type filaments.

3. DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention.

This invention is further developed on the above conventional technologyand the object is to obtain easily sheath-core type super microfilamentsby simple and convenient method without the need of special,high-accuracy and high-level apparatus. And the other object is toenable stable manufacturing of sheath-core type filaments such as hollowfilaments, optical filaments and conjugate filaments in high quality andfine diameters of filaments. Moreover, the other object is to providesheath-core type filaments in which a drawn portion of the drawn hollowsuper microfilaments, drawn optical super microfilament and the like andun-drawn original filaments are connected in a unified manner. Further,the other object is to enable the manufacturing of long fiber non-wovenfabrics consisting of sheath-core type filaments such as hollow suppermicrofilaments and conjugate super microfilaments.

Means to Solve the Problems

This invention has been accomplished to achieve foregoing objects andthe characteristics as the manufacturing method are shown below. Thisinvention concerns a manufacturing method of the sheath-core typefilaments which are provided an applied tension of 10 MPa or less andare drawn at the draw ratio of 100 times or more by heating withinfrared beams. Also this invention relates to a manufacturing method ofdrawn sheath-core type filaments in which said tension is provided bythe own weight of the original sheath-core type filaments. And thisinvention concerns a manufacturing method of the drawn sheath-core typefilaments in which the said infrared beams are irradiated withinup-and-down 4 mm or less of axial direction at the center of theoriginal sheath-core type filaments and are the irradiation from atleast 2 directions or more. Also this invention concerns a manufacturingmethod of the drawn sheath-core type filaments in which said infraredbeam is a laser beam. And this invention concerns a manufacturing methodof the drawn sheath-core type filaments in which said originalsheath-core type filaments are delivered by blowing ducts and guided tosaid infrared beams. Also this invention relates to a manufacturingmethod of the drawn sheath-core type filaments in which said originalsheath-core filaments are equipped with a guiding tool to restrict theposition of the original sheath-core type filaments before said originalsheath-core type filaments are heated by the infrared beams. And thisinvention concerns a manufacturing method of drawn sheath-core typefilaments in which the drawn sheath-core type filaments are connected tothe original sheath-core type filaments are obtained by stopping theinfrared irradiation during said drawing process and taking out theproducts in the situation that oriented filaments have been connected tothe original sheath-core type filaments. Also this invention relates toa manufacturing method of drawn sheath-core type filaments in which thesaid drawn sheath-core type filaments are heated by a zone heaterdescribed below. And this invention concerns a manufacturing method ofdrawn sheath-core type filaments in which said drawn sheath-core typefilaments are further drawn. Also this invention relates to amanufacturing method of drawn sheath-core type filaments in which pluralnumbers of the drawn sheath-core filaments reeled off simultaneously arefurther drawn and wound-up in a unified manner. And this inventionrelates to a manufacturing method of non-woven fabrics consisting of thedrawn sheath-core type filaments in which said drawn sheath-core typefilaments are collected on a running conveyer. Further, this inventionrelates to a drawing starting method of the drawn sheath-core typefilaments in which said original filaments are drawn with tensionprovided by the own weight and then drawn by predefined wind-up speed ina manufacturing method of said drawn sheath-core type filaments.

Also this invention is conducted to achieve the above objects and thefeatures as a manufacturing apparatus are shown in the following. Thisinvention concerns a manufacturing apparatus of drawn sheath-core typefilaments which have a supply device of the original filamentsconsisting of the sheath-core type filaments, an infrared ray heatingdevice that are composed to heat within up-and-down 4 mm of axialdirections at the center of the original filaments by the irradiation ofthe infrared beams from plural spots (directions) and the means tocontrol the heated original filaments to be drawn 100 times or more byproviding an applied tension of 10 MPa or less. And this inventionrelates to a manufacturing apparatus of the drawn sheath-core typefilaments in which said infrared beam is a laser beam radiated by alaser emitter. Also this invention relates to a manufacturing apparatusof drawn sheath-core type filaments in which the radiation means fromplural directions of said infrared beams are ones reflecting theirradiated beam from one direction using mirror. And this inventionrelates to a manufacturing apparatus of drawn sheath-core type filamentsin which the radiation means from plural directions of said infraredbeams are the beams from plural infrared beam emitters. Also thisinvention concerns a manufacturing apparatus of drawn sheath-core typefilaments in which the laser is a carbon dioxide gas laser having said alaser power density of 10 W/cm² or more. Further, this invention relatesto a manufacturing apparatus of drawn sheath-core type filaments inwhich said original sheath-core type filaments are provided with aguiding tool to regulate the position of the sheath-core type filamentsbefore heating by said infrared beams. Also this invention concerns amanufacturing apparatus of drawn sheath-core type filaments in whichsaid guiding tool has a position control device that can finely adjustthe guiding position of said original sheath-core type filaments.Further this invention relates to a manufacturing apparatus of the drawnsheath-core filaments in which it is composed that a blowing duct isdescribed above said original sheath-core filaments are heated by saidinfrared beam and the original sheath-core filaments are delivered bythe blowing duct.

Moreover, this invention has been conducted to accomplish foregoingobjects and the following shows the features as drawn sheath-core typefilaments. This invention concerns drawn sheath-core type supermicrofilaments in which said drawn sheath-core type filaments are hollowfilaments consisting of sheaths only of which insides are gas, and aouter diameter of the drawn hollow filaments are 10 μm or less. Also,this invention relates to the drawn sheath-core type supermicrofilaments in which said drawn sheath-core type filaments are thehollow filaments for dividual fibers having many cracks in alongitudinal direction of the drawn hollow filaments. Furthermore, thisinvention concerns drawn sheath-core type super microfilaments in whichsaid drawn sheath-core type filaments are the micro-porous-film hollowfilaments having many micro-pores on a wall of the drawn filaments.Also, this invention concerns drawn sheath-core type supermicrofilaments in which core components of said drawn sheath-core typefilaments are consisted of polymers that have light transmittance formain component of 85% or more, and are optical filaments with thefilament diameter of 30 μm or less. Moreover, this invention relates todrawn sheath-core type super microfilaments in which core components ofthe said sheath-core type filaments are quartz series glass or fluorideglass and are optical filaments with a filament diameter of 10 μm orless. Further, this invention relates to the drawn sheath-core typesuper microfilaments in which said drawn sheath-core type filaments arethe conjugate filaments and the sheath components of conjugate filamentsconsist of adhesive polymers. Also, this invention relates tosheath-core type filaments in which said original sheath-core typefilaments and said drawn sheath-core type filaments are the connectedoptical filaments. Moreover, this invention concerns sheath-core typefilaments in which said original sheath-core type filaments and saiddrawn sheath-core type filaments are the connected hollow filaments.

This invention relates to the drawn sheath-core type filaments. Thefilaments are the fibers that have substantially continuous length andare distinguished from staple fibers that consist of short length (fromseveral millimeters to several centimeters). The sheath-core type meansthe filaments that are actively differentiated structure at skin portionand inside core portion in cross sections of filaments. The word“actively” means that it is not included skin structure and so on thatspun filaments from homogeneous systems generate at spinning and drawingstages.

The hollow filaments in this invention are formed of sheaths only andcores consist of gases but included in the sheath-core type filaments ofthis invention. And, in a case filaments have plural hollow portionsinside, called a lotus root type; is also included in the sheath-coretype filaments of this invention.

The hollow filaments of this invention consist of polymers used asfibers for clothes such as poly(ethylene terephthalate) (PET),polyamide, polypropylene and polyvinyl alcohol and have been usedconventionally for the purpose of light weight, heat insulation andthermal retention. But, by making these to super microfilaments simplyand conveniently by this invention, performance such as fineness oftexture for clothes, improved gloss and printability and possiblepresentation of water proof property are further increased and these arehigh-grade and high-quality filaments. Also, the hollow filaments havingmany cracks for manufacturing the dividual fibers are included as theother example of the hollow filaments. The fibers, divided afterdrawing, having more fine and complicated cross section can bemanufactured by forming super microfilaments simply and conveniently bythis invention. Further in this invention, the hollow filaments(micro-porous hollow filaments) that have many micro-pores (pore-size:from several tens angstroms to several micrometers) on walls calledhollow fiber membranes (micro-porous-film hollow fibers) are alsoincluded. The micro-porous hollow filaments are formed simply andconveniently into the super microfilaments according to drawing of thisinvention and further thickness of the membrane is reduced andseparating efficiency is improved by drawing. And shapes of pores arethin and long by drawing, so the pores are finer that more delicateseparation is enabled and performances as gas separation membranes areincreased.

The optical filaments consist of cores that are made of high lighttransmittance materials and sheaths (clad) that are made of thematerials of a lower refractive index than the core and are thefilaments of sheath-core structure. Though there are organic series andinorganic series in the optical filaments, this invention includes bothof them. The optical filaments of this invention have the lighttransmittance of 85% or more, preferably 88% or more, further preferably90% or more and the most preferably 92% or more. The lower lighttransmittance materials than the core component is used for the sheathcomponent. Still, this light transmittance is measured in a visiblelight range including 200 μm.

The optical filaments of this invention are a thin and long line fortransmitting light inside of the filaments, usually also called opticalfibers or optical waveguides. The optical filaments normally are thefilaments of the sheath-core structure consisting of the core that ismade of materials of the high light transmittance and the sheath (clad)that is made of the materials of a lower refractive index than the core.And, for the sheath-core structure, there are step index type in whichthe core and the sheath are clearly separated and the light advancesreflecting at a boundary of the core and the sheath, Greaded Index typein which the central portion of filament has the highest refractiveindex and it is gradually lowered toward periphery so that the lighttried to go out advances gathering at a central portion, single modetype in which the light advances the central portion mainly as thecentral portion diameter of the core is made 10 μm or less. As thisinvention can easily manufacture fine diameter filaments from largediameter filaments, especially suitable for manufacturing single modetype filaments from step index type filaments. The drawn opticalfilaments of this invention improve point by point resolution of animage sensor and the like according to be super microfilaments bydrawing and enable an apparatus to be compact as fiber bundles are moreflexible and also thin and flat.

The core component of drawn optical filaments of this invention ispreferably made of one kind of polymer selected from poly-methylmethacrylate, polycarbonate, polystyrene and poly-trimethyl pentane asthe main component. Because these polymers have good light transmittanceand high refractive index. The main component means that the componentexceeding 50% (weight percent, hereinafter the same); preferably 70% ormore and the most preferably 90% or more consists of these polymers.Also, it is possible to use these polymers that are modified with theother chemical species. And, it is characterized in that the sheathcomponent of the optical filaments is a fluorine-containing polymer. Thefluorine-containing polymers are low in the refractive index that it isvery useful for the sheath component of the optical filaments. Thefluorine-containing polymer is referred to the polymers containing 2% ormore, preferably 5% or more fluorine atom in it.

In organic series optical filaments of this invention, filamentdiameters are preferably 30 μm or less, more preferably 20 μm or lessand the most preferably 10 μm or less. Conventionally, organic seriesoptical filaments of such small diameter have been difficult tomanufacture, but it is characterized in that these can be simply andconveniently manufactured by this invention and that manufacturing ofthe filaments connected to the original filaments of larger diameter isalso possible.

As inorganic series optical filaments of this invention, it ischaracterized in that the core components are quartz glass or fluorideglass. The quartz glass is preferred in long distance communication andthe fluoride glass is further preferred in high performance field.

In this invention, various kinds of conjugate filaments spun fromconjugate spinning dies are also included. The conjugate filaments arealso called composite filaments (or composite fibers). As an example ofthe conjugate filaments of this invention includes filaments of whichthe core is strength member polymers such as polyethylene terephthalate,nylon and polypropylene and the sheath is an adhesive layer consistingof polymers that have lower melting point than the core such as modifiedpolyester, modified polyamide or modified polyolefin, that thesefilaments have adhesiveness. And as the other example of conjugatefilaments, there are also hygroscopic filaments in which the cores arethe foregoing strength member polymers and the sheaths consist of layersof polymers having hygroscopic properties such as polyamide andpolyvinyl alcohol. Moreover, the conjugate filaments are used also forfilaments generating crimp by unevenly distributing the position of thecore from the center of the cross section and generate shrink afterdrawing. Although these conjugate filaments have been usedconventionally, their performances are further improved and make themhigh-grade and high-quality ones by being super microfilaments simplyand conveniently by this invention.

This invention provides means for drawing of the original sheath-coretype filaments. The original sheath-core type filaments in thisinvention may be already manufactured as the sheath-core type filamentsand wound-up on bobbins and the like, or sheath-core type filaments tobe the material for the drawing means in this invention which are formedinto the sheath-core type filaments from molten or dissolved sheath-coretype filaments by cooling or coagulation in the spinning process, andused successively in the spinning process.

The original sheath-core type filaments of this invention are heated toan appropriate temperature for drawing by infrared beams irradiated frominfrared heating means (including a laser). The infrared rays heat theoriginal sheath-core type filaments but the range to be heated to anappropriate temperature for drawing is heated preferably withinup-and-down 4 mm in axial directions of the filaments at the center theoriginal sheath-core type filaments, further preferably 3 mm or less andthe most preferably 2 mm or less. This invention enables the drawingwith high molecular orientation by the rapid drawing in the narrowregion and that it is possible to decrease breakage of drawing even inthe super high drawing ratio. Yet, the irradiation of infrared beams inthis case shall preferably be irradiated from plural directions. Becausethe originally difficult to draw filaments by asymmetry heating of thesheath-core type filaments, the heating from one side only of filamentsmake it more difficult to draw. If the original filaments are the hollowfilaments, heating from one side only especially make it difficult todraw by its thermal insulation property. Such irradiation from pluraldirections can be achieved by the irradiation of plural times along apassage of the original filaments by reflecting the infrared beam withmirrors. The mirrors of rotating type, not only fixed types, such aspolygon mirrors can be used.

And as the other means of irradiation from plural directions, there aremeans to irradiate light sources from plural light sources to theoriginal filaments from plural directions. It is possible to be the highpowered light sources by using plural laser emitters which arerelatively small laser light sources and are stable and not expensive,that the method of using plural light sources is useful as thesheath-core type filaments of this invention need high watt density.

The wave length of the infrared rays is said to be from 0.78 μm to 1 mmbut a near infrared region about from 0.78 μm to 20 μm centering on theabsorption at 3.5 μm for C—C bonds of polymeric compound is particularlypreferred. For the infrared rays, heating heaters referred to a spotheater or a line heater of narrowing the focal point into a line or spotshape by a mirror or a lens thereby narrowing the heating area for thesheath-core type filaments to up-and-down 4 mm or less in an axialdirection can be used. Particularly, the line heater is suitable in acase of heating the plural sheath-core type filaments simultaneously.

For the infrared heating in this invention, laser heating isparticularly preferred. Among all, a carbon dioxide gas laser with awave length of 10.6 μm and a YAG (Yttrium-Aluminum-Garnet series) laserwith a wavelength of 1.06 μm are particularly preferred. Also, an argongas laser can be use. Since the laser can restrict the radiation rangesmaller and the energy is concentrated to a specified wavelength,wasteful energy is decreased. The carbon dioxide gas laser of thisinvention has the power density of 10 W/cm² or more, preferably 15 W/cm²or more, further preferably 20 W/cm² and the most preferably 30 W/cm² ormore. This is because the super high ratio drawing of this invention isenabled by concentrating the high power density energy to a narrowdrawing region. Still, in this invention, although the originalfilaments are irradiated from the plural directions, the power densityfrom each direction is added and shown in this case.

Generally, the drawing is carried out by heating the sheath-core typefilaments and the like to an appropriate drawing temperature andapplying a tension thereon. The applied tension in drawing of thisinvention, characterized in that drawing is conducted by the tensionprovided by the own weight of filaments. This is different in theprinciple, from usual drawing where drawing is conducted by the tensionprovided by the difference of speeds between rollers and by the tensioncaused by wind-up. In this invention, an optimal applied tension can beselected by changing the own weight of the sheath-core filaments appliedto the heated portion (determined depending on the free falling distancefrom the heated portion) by the change of the free falling distance. Inthe usual drawing between rollers, it is difficult to control the drawratio as large as 100 times or more. It is the feature of this inventionthat the ratio can be controlled easily by a simple and convenient meansof distance. Such the tension by the own weight can be obtained by therange of 10 Mpa or less shown in the following.

Further, the tension in this invention is extremely reduced level, andthe drawing is conducted by setting an applied tension to 10 MPa orless, preferably 3 MPa or less, further preferably 1 Mpa or less and themost preferably 0.3 MPa or less. If the applied tension exceeds 10 Mpa,the breakage at the drawing is liable to occur and the range of theapplied tension as described above is preferred for drawing at a highdraw ratio. With such small drawing tension, the extremely high drawingratio such as 100 times or more, depending on the condition 1000 timesor more or 10,000 times or more can be realized. Because, drawing isconducted within an extremely narrow drawing region while keeping anextremely high drawing temperature of the melting point or thereabout,so that the sheath-core type filaments can be deformed with no breakage.In the usual drawing for synthetic fibers between rollers, the fibersare drawn at an applied tension of several ten MPa to several hundredMPa. The feature of this invention resides in drawing within a rangegreatly different therefrom.

In this invention, it is characterized in that the filaments are drawnat a super high ratio of the obtained drawn sheath-core type filamentsas 100 times or more, preferably 200 times or more, further preferably500 times or more and the most preferably 1,000 times or more areconducted. Considering that the draw ratio of a usual synthetic fiber is3 to 7 times, and even in super drawing of PET fibers, it is about tenand several times. Especially in functional fibers such as hollow fibersand optical filaments, conjugate filaments and the like, drawing of thesuper high draw ratio like this invention is not conducted as there ispossibility to damage the function of filaments in such the super highdraw ratio. This invention has a feature in that drawing within anextremely narrow zone is enabled and, accordingly, the drawingtemperature can be increased to the melting point or thereabout of theoriginal sheath-core type filaments which decreases the drawing tension,and that means capable of controlling the small drawing tension and thesuper high draw ratio has been found. Since the drawing at the superhigh draw ratio is possible, this enables manufacture of the sheath-coretype super microfilaments with a diameter of 30 μm or less, further 10μm or less and further 5 μm or less, as well as increase the productionspeed for manufacture of the sheath-core type filaments to severalhundred times, which is significant in view of the productivity.

In this invention, there is a case that drawing is conducted with aswelled portion larger than the diameter of the original sheath-coretype filaments at a drawing starting portion where it is drawn by theinfrared beam. Such a peculiar phenomenon has not yet been observed inusual drawing for synthetic fibers. It is considered that the phenomenonis derived from that the drawing temperature is increased to the meltingpoint or thereabout of the original sheath-core type filaments anddrawing in the narrow zone is enabled. As described above, by drawingwith the swelled portion, it is enabled to draw at a draw ratio of 100times or more, or 1,000 times or more and in a suitable condition 10,000times or more.

In a case of heating original sheath-core type filaments in thisinvention by the infrared beam, continuously drawn filaments are formedby moving the original filaments against the infrared beam. For themoving of the original filaments, two means are provided by thisinvention. One of them is a method in which original filaments are movedrelatively to the infrared beam (batch method) by a transfer device ofthe gripper, where the original filaments are held with a gripper. Theother one is a method in which the original filaments are continuouslydelivered (continuous method) by a supply means of the originalfilaments.

In the batch method, the original filaments are held by the gripper andthe original filaments move relatively against the infrared beam by thetransfer device of the gripper. The gripper may be some kind of a chuck,but there is a case that the gripper is connected to a part of thetransfer device. The typical transfer device is a crosshead moved by arack-and-pinion system, but the device may be simple rotating spiralscrew and the like. Also, it is possible to guide to a suitable positionof the infrared beam by guiding the original filaments with tackles andso on to move the original filaments easily.

In the continuous method of this invention, drawing is conducted to theoriginal sheath-core type filaments delivered from the supplying means.As for the supply means, various types can be used if these can supplythe sheath-core type filaments at constant supplying speed with niprollers, driven roller groups and the like.

In both the batch and continuous methods, it is preferable to provide aguiding tool which controls the position of the original filaments justbefore the infrared beam hit original filaments. Depending on the exitshape of a blowing duct of the continuous method it is possible to havesuch function, but the blowing duct shall focus on air flowing of gasdelivering sheath-core filaments and easiness of passing sheath-coretype filaments, and after that to control the position of sheath-coretype filaments is preferable by the simple and convenient guiding tool.As the guiding tool, a narrow duct or groove, a comb or a combination offine bars may be used. Also foregoing tackles can achieve roles of theguiding tool of this invention.

The just before position of the infrared beam hitting the originalfilaments is preferably 100 mm or less, further preferably 50 mm or lessand the most preferably 20 mm or less. The heating by infrared beam ofthe original filaments characterizes in that the heating is conductedextremely narrow range and the position of sheath-core type filamentsare required to be restricted for enabling the heating of the narrowrange. Although the guiding tool is not required in conventionalordinary drawing as the drawing tension is large, but in this inventionas the drawing tension is small and the drawing ratio is large, and verylittle fluctuation and variation of the drawing point affect thestability of the drawing that to provide the guiding tool just beforethe drawing point greatly contributes to the stability of drawing. Theguiding tools for this invention, a narrow duct and groove, a comb or acombination of fine bars may be used.

In the above guiding tools, it is desirable to have a position controlmechanism to be able to adjust finely the position of the guiding tool.For precisely fitting a running position of filaments to a narrow regionof laser beam, the guiding tool shall necessary be controlled theposition in XY directions.

The original sheath-core type filament delivered by the supplying meansof filaments are desirable to be delivered further through the blowingduct by a gas flowing the running direction of the original sheath-coretype filament in the blowing duct. As for the gas flowing in the blowingduct, the gas of room temperature is used usually but when pre-heatingof the original sheath-core type filaments is desired, heated air isused. And if the original sheath-core type filaments are prevented to beoxidized an inert gas such as nitrogen or the like is used and ifscattering of water is protected a gas containing water vapor or wateris used. Still, the blowing ducts shall not necessary be a tubular shapebut being a groove shape, if original sheath-core type filaments canflow together with the gas through in these. The cross section of theduct is preferably circular but may be rectangular or other shape. Thegas flow through the duct may be supplied from one of a branched ducts,or may be supplied from an outer duct to an inner duct through aperturesand the like using a double walled duct. An air jet interlacing nozzlefor filaments used for interlace spinning or Taslan fabrication ofsynthetic fibers is also used for the blowing duct in this invention.And in a case of drawing by free falling as non-woven fabricsmanufacturing in this invention, filaments may be provided the drawingtension by air momentum according to the blowing duct of this invention.

In drawing of the sheath-core type filaments in this invention, it ischaracterized in that plural numbers of the original sheath-core typefilaments are gathered together and can be drawn in the same infraredbeam. Usually, if the plural numbers of original filaments are drawntogether, agglutination among the drawn filaments occurs but thesheath-core type filaments can be drawn without the agglutinationdepending on composition of the sheath component. For example, it issuch a case that the sheath components of the optical filaments arefluorine series polymers. And, by the guiding tool just before thedrawing point, it can be made also not to contact among plural filamentsat the drawing point. The plural numbers of filaments mean that thedrawing could be conducted for 2 or more and in some cases even 5 ormore filaments.

The drawn sheath-core type filaments of this invention are wound-uparound a bobbin or cheese in a following process into products ofbobbin-wound or cheese-wound form. In these wind-up processes, the drawnsheath-core type filaments are preferably wound-up while beingtraversed. This is because uniformly wound-up form can be ensured bytraversing. In the sheath-core type super microfilaments, occurrences ofbreakage of filaments or fluff result in a most significant problem. Inthis invention, since the filaments are highly molecular oriented andthe drawing tension is small, the filaments can be wound-up with a smallwinding tension, it is characteristics of this invention to decreasealso occurrences of breakage of filaments or fluff. Yet, when the pluralfilaments are drawn and wound-up simultaneously it is possible towind-up twisting by a twister but it is preferable to wind-up entwiningamong filaments by an interlace method as running speed of the filamentsof this invention is fast.

Subsequent to the drawing step of this invention, a heating devicehaving a heating zone may be disposed to apply a heat treatment to thedrawn sheath-core type filaments. Heating can be conducted by passingthem through a heating gas, radiation heating such as infrared rayheating, passing them over a heating roller, or a combination of them.The heat treatment can provide various effects such as reduction ofthermal shrinkage of the drawn sheath-core filaments, increase in thedegree of crystallinity to decrease the aging change of the sheath-coretype filaments or improve the Young's modulus. In the case of non-wovenfabrics of this invention, the heat treatment may also be applied on aconveyor.

The drawn sheath-core type filaments of this invention can be wound-upafter additional drawing. For the drawing in the subsequent step,drawing means by the infrared ray used in the previous step can also beused. In a case where the filament has already been drawn at asufficiently high draw ratio in the previous step and the sheath-coretype super microfilaments have already been obtained, inter-rollerdrawing such as by usual godet rollers, pin drawing and zone drawing mayalso be used.

Non-woven fabrics consisting of the drawn sheath-core type filaments canbe manufactured by accumulating the drawn sheath-core type filaments ofthis invention on a running conveyor. Especially in this invention, itis significant that non-woven fabrics consisting of the supermicrofilaments of the hollow filaments and the conjugate filaments canbe manufactured simply and conveniently. In recent years, non-wovenfabrics have been demanded vigorously in various fields taking notice onthe characteristics peculiar to the non-woven fabrics not merely assubstitutes for woven fabrics. Among them, non-woven fabrics of supermicro fibers include melt blown non-woven fabrics which are prepared byblowing off molten filaments by hot blow to form filaments of 3 μm orthereabout and then accumulating them on a conveyor to form non-wovenfabrics. They are used mainly for air filters. However, filamentsconstituting the melt blown non-woven fabrics have lower strength thanusual non-drawn fibers as 0.1 cN/dtex or thereabout, in which a numberof small lumps of resins called as shots or wads are present. Thenon-woven fabrics consisting of the drawn sheath-core type filaments ofthis invention have strength equal with or superior to that of usualsynthetic fibers while having a diameter of about 3 μm or thereaboutlike the melt blown non-woven fabrics because the sheath-core typefilaments are highly oriented. And it is possible to prepare non-wovenfabrics without containing shots and wads at all and to be non-wovenfabrics having high functions by further consisting of the hollowfilaments and the conjugate filaments.

Non-woven fabrics of this invention, adding to effects of being finetexture, and improved luster and printability by being the supermicrofilaments, these can also have characteristics of light weight,heat insulation, thermal retention, water repellency and the like byconsisting of the hollow filaments and adhesiveness, distinctive touch,bulkiness and so on by consisting of the conjugate filaments. Non-wovenfabrics usually require any interlacing or entwining among fibers.However, in this invention, since the diameter of filaments areextremely small, the number of the sheath-core type filaments per unitweight is extremely increased and the sheath-core type filaments areinterlaced by vacuum suction below the conveyor and there are many casesthat simple pressing upon accumulation of the sheath-core type filamentson the conveyor is sufficient, with no particular interlacing orentwining process like melt blown non-woven fabrics. Naturally, methodssuch as thermal embossing, needle punching or adhesive bonding conductedin usual non-woven fabrics may also be used, which may be selecteddepending on the application use. In the filter usage as a majorapplication use of super micro fiber non-woven fabrics, collectingefficiency can be increased outstandingly by applying electrostatictreatment to the non-woven fabrics and non-woven fabrics of thisinvention can also be applied by electrostatic treatment to the field ofthe filters. When filaments are accumulated on the conveyor in themanufacture of the non-woven fabrics of this invention, negativepressure is applied at the back of the conveyor and the flow of airunder air suction by negative pressure or the flow of air by thepositive use of an air sucker sometimes acts as tension for drawing inthe sheath-core type filaments drawing, which is also included in thedrawing tension of this invention.

In the drawn sheath-core type filaments of this invention, the drawnfilaments can also be provided in the form of connected to the un-drawnfilaments. The filaments of this form are especially preferable in abatch method although may be provided in a continuous method. And, asmaterials for filaments, the optical filaments and the micro-porous-filmhollow filaments are especially preferred. By being the drawn filamentsconnected to the un-drawn filaments in the optical filaments, theseenable to hit strong light on a pin point collecting light from largerarea, and as these can be used when light of a light source is weak, soit is useful for a fiberscope and the like. Usually, in such cases, aconnecting device is necessary between a light condensing device and theoptical filaments but there are defects that the connecting is difficultand the device is expensive when filaments are fine. Also when theun-drawn portion is connected to the drawn micro-porous-film hollowfilaments, supplying portion of gasses and the like are large that thegasses and the like are supplied at these portion simply andconveniently and there is an advantage to be able to supply gasescontinuously thereafter to the micro-porous-film hollow supermicrofilaments without the need of any connecting devices. Yet,filaments in this form that the original filaments are connected to thedrawn sheath-core type filament can be obtained by taking out productsthat the original filaments are connected to the drawn filaments stateby stopping the infrared beam irradiation during the drawing. In thiscase, the connecting refers to continuously unified status without usingadhesive and other means.

Still, the draw ratio (λ) in this invention is represented by thefollowing equation based on the diameter d_(o) for the original filamentand the diameter d for the filament after drawing. In this case,calculation is performed assuming the density of filament as constant.The diameter measurement of the filament is conducted by a scanningelectron microscope (SEM) based on photograph taken at 100×, 350× or100×, with respect to average values for 10 points.λ=(d _(o) /d)²Advantageous Effects of the Invention

In this invention, concerning the sheath-core type filaments such ashollow filaments, optical filaments, conjugate filaments and etc., itwas possible to obtain the super microfilaments easily by simple andconvenient means without requiring the special, high-accuracy andhigh-level devices. These sheath-core type hollow super microfilamentsare realized by the super high draw ratio of 100 times or more andenabling to provide the methods to realize such high ratio drawing meannot only the sheath-core type super microfilaments can be obtainedsimply and conveniently but also possible to produce the hollow supermicrofilaments at high speed that the significance from a productivityside is large.

When the sheath-core type super microfilaments by this invention are thehollow filaments, adding to the property of light weight, thermalretention, heat insulation and the like that the hollow filaments have,being the super microfilaments the texture is fine, luster andprintability are improved and further shall be high-grade andhigh-quality. The hollow filaments are used for swim wear in recentyears; the properties of thermal retention, floating on water anduneasiness to see-through are utilized. By making these to the supermicrofilaments, the commercial value is increased by being fine texture,increasing the water repellency also and improving the luster and theprintability. If the hollow filaments are the hollow filaments for thedividual fibers, the finer filaments may be manufactured and are hollowfilaments with the cross section of complicated shape. In a case thatthe hollow filaments are the micro-porous-film hollow filaments,separation efficiency is improved as the film thickness is thinned bydrawing. And, as the shape of pores is thinner and longer, and finer bydrawing that separation efficiency can be improved. Further, because theun-drawn parts are connected to these drawn micro-porous-film hollowfilaments, supply of raw material gas and the like is easy as asupplying portion and so on of gas is large and the connection to themicro-porous-film hollow super microfilaments is possible without needof any special connecting device that the device is not expensive and itwas possible to make the device compact.

In a case that sheath-core type super microfilaments of this inventionare optical filaments, point by point resolution is increased by usingfor an image sensor and this leads to an improvement of performances ofthe sensor and diagnosis equipment. Also, as it is super microfilaments,fiber bundles are flexible and thin flat that it is possible to make theequipment compact. Moreover, since un-drawn portions are connected tothese drawn optical filaments, strong light can hit on a pinpointcondensing light in a large area and performances as a fiberscope andthe like are improved. Also, these were optical filaments that theefficiency of condensing light is good even light of a light source isweak. And, conventionally connection of condensers and optical filamentswere difficult because filaments were fine. But, in this invention sincedrawn filaments and un-drawn portion are connected, there is no need ofthe connecting portion and as an expense for the connecting device isalso unnecessary that the cost is reduced and the devices is compact.

When the sheath-core type super microfilaments of this invention are theconjugate filaments, the performances as adhesive filaments, absorbentfilaments and the crimp filaments of the conjugate filaments are furtherimproved by filaments are super-micro, and are high-grade andhigh-quality.

Moreover, long fiber non-woven fabrics consisting of the hollow supermicrofilaments and the conjugate super microfilaments could bemanufactured according to this invention. There are melt blown non-wovenfabrics as non-woven fabrics consisting of the sheath-core type supermicrofilaments which are on the market but the filaments have notsufficient strength and there were problems to mingle with small lumpsof resins called a shot or a wad. However, the non-woven fabrics of thisinvention have no such defects and make the non-woven fabrics higher ingrade and higher in quality, cooperating together the characteristicssuch as thermal retention and light weight that hollow filaments have,the properties of adhesiveness, bulkiness and moisture absorbency thatthe conjugate filaments have and the quality of fineness of texture,gloss and improved printability that super microfilament have.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of the process manufacturing the drawnsheath-core type filaments of this invention in a batch method.

FIG. 2 shows a schematic view of the process manufacturing the drawsheath-core type filaments in a continuous method.

FIG. 3A shows a plain view of an example of mirror arrangement toirradiate the infrared beams from plural directions to the originalsheath-core type filaments of this invention.

FIG. 3B shows a side view of an example of mirror arrangement toirradiate the infrared beams from plural directions to the originalsheath-core type filaments of this invention.

FIG. 4 shows a plain view of the other example to irradiate the infraredbeams from the plural directions to the original filaments in case ofhaving plural light sources.

FIG. 5 shows a schematic view of a process in case of re-drawing pluralnumbers of the drawn sheath-core type filaments of this invention.

FIG. 6 shows a schematic view of the various blowing ducts used in thisinvention.

FIG. 7 shows a schematic diagram of the process manufacturing non-wovenfabrics consisting of the drawn sheath-core type filaments of thisinvention.

FIG. 8 shows a graph for the experimental results of variation betweenoutside diameters and inside diameters of the filaments according todrawing of the hollow filaments of this invention.

FIG. 9 shows a scanning electron microscope photograph (1000×) of thedrawn hollow filaments of this invention.

FIG. 10A is a polarizing microscope photograph of the drawn hollowfilaments of this invention shown by a photograph (100×) of a drawingstarting point.

FIG. 10B is a polarizing microscope photograph of the drawn hollowfilaments of this invention shown by a photograph (100×) of the drawnfilaments.

5. DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, the examples of modes to carry out this invention aredescribed based on the drawings. FIG. 1 shows an example of theapparatus in the batch method of this invention. The originalsheath-core type filaments 1 are gripped by a gripper 3 fixed on atransfer device 2 moved by rack-and-pinion method. According to a guiderail 4 consisting of a spiral screw moves downward at a constant speedby rotation of a motor, the original filament 1 moves downward at aconstant speed. A laser beam 6 from a continuous carbon dioxide gaslaser emitter 5 is adapted to irradiate a specific position of themoving original filaments 1. In the drawing, to constantly keep stablethe infrared irradiation position of the original filament, tackles 7 a,7 b are provided to up-and-down of the infrared beam irradiationposition of the original filaments and disposed to guide the originalfilaments. The original filaments irradiated infrared rays are drawn bythe own weight or a tension of 10 MPa or less and shall be the drawnsheath-core type filaments 8. The drawn sheath-core type filaments 8 areadded a load 9 if necessary or wound-up by a winding reel. Moreover, thedrawing tension may be measured simply and conveniently by using thegripper 3 as a chuck of a tension tester that is directly connected to aload cell of a tension tester. The batch method of FIG. 1 is especiallyuseful when obtaining filaments connected the original sheath-core typefilaments with the drawn filaments.

FIG. 2 shows an example of a process for the continuous method of thisinvention. The original sheath-core type filament 1 is reeled off from astate of wound around a reel 11, passed by way of a comb 12 anddelivered at constant speed from reel off nip rollers 13 a and 13 b. Thedelivered original filament 1 is sent by a blowing duct 14 and thenfalls down at a constant speed while being regulated for the position bya guiding tool 15. The blowing duct 14 adapted such that air guidedalong arrow “a” is introduced to a channel of the original filament 1and the filament is sent by flow of air. Still, the use of the blowingduct 14 can also be omitted. The guiding tool 15 is used for accuratelydetermining the laser irradiation position and the running position ofthe filament. While a hypodermic needle with an inner diameter 0.5 mmwas used in the drawing, a narrow pipe, a comb or snail-wire shown inFIG. 7 can also be used. A laser beam 6 is irradiated to a zone heater Mof a predetermined width by a laser emitter 5 to the running originalfilament 1 just below the guiding tool 15. The filament is heated by thelaser beam 6 and drawn by the tension given by the own weight of thefilament and the velocity of flow of air delivered from the blowingduct, and falls down as a drawn sheath-core type filament 16 and ispreferable to pass through a heat treatment zone 17 formed in thefalling path. The drawn sheath-core type filament 16 passes along atackle 18 and then wind-up by way of take-up nip rollers 19 a and 19 baround a wind-up reel 20. In this case, the channel of the drawnsheath-core type filament 16 to the tackle 18 includes a case where itis drawn as a trace “p” of a free falling of the filament, a case whereit is drawn as a linear trace “q” to the tackle 18 and a case where itis drawn as an intermediate trace thereof. In a case where it is drawnby the own weight of the drawn sheath-core type filament 16 in the trace“p”, the flow of air from the blowing pipe 14 is sometimes added to thedrawing tension, which is also included within a category of drawing byown weight. In the trace “q” and at the intermediate position of thetrace “p” and trace “q”, the wind-up tension exerts on the drawingtension in which the drawing tension is preferably 10 MPa or less. Thedrawing tension may be measured by a tension measuring mechanismdisposed to the tackle 18 but as an another method, it can be estimatedbased on the relation of the same supplying speed, the laser irradiationcondition and the draw ratio by the load cell measurement of above batchmethod. Before wind-up around the take-up and wind-up reel 20, thefilament can be further drawn between the heated drawing rolls 21 a, 21b and the drawing rolls 22 a and 22 b by a speed ratio of the drawingrolls 21 and 22. The heat treatment zone 17 for the drawn sheath-coretype filament in this case is preferably disposed subsequent to thedrawing roller 22. Also, when the plural original filaments are drawnsimultaneously, it is preferable to have been air interlaced amongfilaments by a interlace method and the like just before the take-upreel.

FIG. 3 shows an example of means to irradiate the infrared beam adoptedin this invention to the original filament from the plural directions.FIG. 3A is a plain view and 3B is a side view. The infrared beamirradiation to the original filament from the plural directions likethis drawing is also conducted in FIGS. 1 and 2, but is omitted to showin FIGS. 1 and 2 as it is complicated and shown representatively in FIG.3. The infrared beam 31 a irradiated from the infrared emitter reachesthe mirror 32 through the region P (inside a dotted line in the drawing)where the original filament 1 passes through and is the infrared beam 31b reflected by the mirror 32, and is the infrared beam 31 c reflected bythe mirror 33. The infrared beam 31 c irradiates the original filamentthrough the region P from 120 degree behind of the first irradiationposition of the original filament. The infrared beam 31 c passed throughthe region P is the infrared beam 31 d reflected by the mirror 34, whichis the infrared beam 31 e reflected by the mirror 35. The infrared beam31 e irradiates the original filament 1 through the region P from anopposite 120 degree behind direction of foregoing infrared beam 31 cagainst the first irradiation position of the original filament. Thus,the original filament 1 can be equally heated from the symmetricalposition 120 degree apart by the three infrared beams 31 a, 31 c and 31e.

In FIG. 4, the other example of the means adopted in this invention toirradiate the infrared beams from the plural directions that is anexample of using plural light sources is shown in a plain view. Theinfrared beam 41 a radiated from the infrared emitter is radiated to theoriginal sheath-core type filament 1. And the infrared beam 41 bradiated from the other infrared emitter is also radiated to theoriginal sheath-core type filament 1. Further, the infrared beam 41 cradiated from the other infrared emitter is also radiated to theoriginal sheath-core type filament 1. Thus, the radiation from theplural light sources can be the high power light sources using theplural laser emitters which are relatively small light sources and arestable and not expensive. Still, a case using 3 light sources are shownin the drawing but 2 are possible and 4 or more can also be used.Especially, when drawing the plural filaments, drawing by using theplural light sources like these is particularly useful.

In FIG. 5, there is shown an example of the sheath-core type filamentsalready drawn by this invention are reeled off the plural number at thesame time and drawing simultaneously. The drawn sheath-core typefilament 52 a, 52 b, 52 c, 52 d and 52 e wound-up around the bobbins 51a, 51 b, 51 c, 51 d and 51 e are each delivered through the blowing duct53 and the pipe 54 and are gathered in an air manifold 55, and isfilaments assembly 56. Still, the sheath-core type filament 52 in theblowing duct 53 and the pipe 54 is not shown in the drawing as iscomplicated. It is preferable that the bobbins 51 are lowered the reeloff tension by rotating at the constant speed because the un-drawnoriginal filament has a low tensile strength and Young's modulus, andfineness of the drawn filament 52 is small that they can not resist thetension. The delivered filaments assembly 56 is adjusted a runningposition to be the center of laser beam by a variable pitch mechanism57. A guiding tool 59 shall preferably guide separately the filamentsfor not to contact the filament each other at a drawing point. Avariable pitch mechanism 57 is provided with the guiding tool 59 and therunning position of filaments are finely adjusted the position by a rack60 and a gear 61. As for the variable pitch mechanism 57, an example toadjust in one direction is shown in the drawing but can be adjusted inXY axis directions by providing a set of gears in a right angle. Thefilaments assembly 56 adjusted the position by the variable pitchmechanism 57 is heated by the laser beam 58 and drawn, and adjusted tothe constant take-up speed by take-up mechanism 62 and wound-up to thewind-up bobbin 63 driven by a motor M. In this drawing the laser beam isshown by one line but is preferably the plural beams shown in FIGS. 3and 4. And, an example of wind-up directly around bobbins is shown inthe drawing but it is preferable to wind-up adding twisting andintertwining among the filaments by the interlacing and the like. Also,an example of re-drawing by the infrared beam is shown in FIG. 5 but there-drawing can use also the other drawing means of ordinary rollerdrawing, zone drawing and so on. Still, the air introduced to theblowing duct 53 and the pipe 54 is guided to a channel of the originalfilament 1 and the filament is delivered by the flow of air, and thetension given by the wind velocity delivering air is added to thedrawing tension of this invention. Yet, FIG. 5 is described as anexample of re-drawing of the drawn filament but used also as the meansfor the plural numbers drawing of the un-drawn original filaments withthe similar mechanism.

FIG. 6 shows examples of various blowing ducts adopted in thisinvention. In FIG. 6A, air introduced from the arrow “a” throughbranched duct 72 joins to a main duct 71 where the filament 1 passesthrough. FIG. 6B shows a double walled duct 73 in which the inside ishollow and air introduced along an arrow “b” is guided through a numberof apertures 74 perforated in the inner wall of the double walled ductto the channel of the filament. FIG. 6C shows an example of a nozzleused as an air interlace nozzle 75 used for interlace spinning in whichthe air is blown from both sides' c1 and c2. Thus, the reason why theair is actively delivered to the running direction of the filaments isnot to disturb the running of filament by the resistance of the guidingtool as the drawing tension is small in this invention and it is alsopossible to add the drawing tension by the momentum of the air whenadding the tension actively with the wind-up tension is not possiblesuch as in a case of manufacturing non-woven fabrics. Also, the nozzlein FIG. 6C can be used at the time of interlace winding after drawing ofthis invention. Yet, the blowing ducts in FIG. 6 show the examples ofthe tubular shape but a grooved shape which is partially opened is alsoused.

FIG. 7 shows an example of manufacturing non-woven fabrics of thisinvention. Multiplicity of the original sheath-core type filaments 1 isattached to a rack 82 in a state wound around bobbin 81 (for avoidingcomplexity, only three filaments are shown). These original sheath-coretype filaments 1 a, 1 b and 1 c are delivered through snail wires 83 a,83 b and 83 c as the guiding tool by the rotation of supply nip rolls 84a and 84 b. The supplied original sheath-core type filaments 1 areheated in the course of falling by the own weight, by line infraredbeams emitted from an infrared emitter 85. The range for the heatingportion “N” by the infrared beams in the running process of the originalsheath-core type filaments 1 is shown by hatched lines. Beams passingthrough the original sheath-core type filaments 1 with no absorption arereflected at a concave mirror 86 shown by dotted line and then returnedto be condensed to the heating portion “N”. A concave mirror is disposedalso on the side of the infrared emitter 85 (in this case, the beamtraveling portion from the infrared emitter has an open window), whichis not illustrated in the drawing. The original sheath-core filaments 1are heated by radiation heat of infrared rays at the heating portion“N”, drawn by the own weight of filaments per se by portion there belowand formed into drawn sheath-core type filaments 87 a, 87 b and 87 c,which are accumulated on a running conveyor 88 to form a web 89. Air issucked in the direction of an arrow “d” by vacuum suction from rear faceof the conveyor 88 to contribute to the stability of running of the web89. The web is pulled by the tension of the negative pressure. “d”exerting on the drawn sheath-core type filament 87 to contribute to theimprovement of attenuation and orientation degree of the sheath-coretype filaments and such tension is also regarded as a portion of thetension caused by the own weight in this invention. Although notillustrated in the drawing, a number of bobbins 81 for the originalsheath-core type filaments 1 are provided in a multi-stage along therunning direction of the conveyor 88, and nip rolls 84 and infraredemitters are provided in a multi-stage to improve the productivity ofthe web 89. In case of providing the supply nip rolls 84 in themulti-stage along the running direction the infrared emitter 85 and theconcave mirror 86 can also be utilized for several stages. Yet, in acase that drawing and orientation are small since the drawing tension bythe own weight of the filaments and the negative pressure from rear faceof the conveyor is not sufficient, guiding the filaments by blowing ductwhen the original filaments 1 are guided to the infrared beam portion,the tension given by the air delivering wind velocity of the blowingduct is also added and used.

EXAMPLE 1

Isotactic (it) polypropylene hollow filaments (filament diameter 280 μm,inside diameter 90 μm) were used as the original sheath-core typefilaments. These filaments were drawn by the drawing apparatus shown inFIGS. 2 and 3. The experimental results for the filament diameter(outside diameter) and the inside diameter of obtained filaments bychanging the supplying speed of the original filaments variously andalso the wind-up speed were shown in FIG. 8. In this case, a carbondioxide gas laser emitter manufacture by Onizuka Glass Co., Ltd. with amaximum power of 10 W was used for the laser emitter. The laser powerdensity was 28.5 W/cm² (1.2 W) at a supplying speed of 0.3 m/min and asthe supplying speed was increased the power density was increased, andwas 52.5 W/cm² (2.2 W) at 0.6 m/min. The laser beam diameter in thiscase was 4.0 mm. The drawn sheath-core type filaments run along thetrace “p” in FIG. 2 and the distance from the laser heating portion M tolowermost position was 120 cm. As shown in FIG. 8, the draw ratio of 100times 6 r more was obtained easily even at a winding speed of 84.8m/min, also the diameter, (outside diameter) of the drawn filamentsreached 7 μm finally and the drawing ratio, too, exceeded 10,000 times.When comparing the ratio of the outside diameter and inside diameter, ifthe supplying speed was low the inside diameter was relatively largeeven the filament diameter was small, and if the supplying speed washigh the inside diameter tended to be small. In FIG. 9, a scanningelectron microscope (SEM) photograph of the thus drawn hollow filamentwas shown. Also, regarding the sample of this drawing process was shownin FIG. 10 by a polarizing microscope photograph to understand theoutside diameter and inside diameter. FIG. 10A showed the drawingstarting portion, in this example the diameter of the drawing startingportion was enlarged although slightly at the drawing start portion.FIG. 10B showed a photograph of the polarizing microscope of the drawnhollow filaments with the outside diameter of 9 μm (draw ratio wasapproximately 850 times). When wide angle x-ray diffraction patterns ofthe drawn filaments were taken, an orientation pattern was clearer thanthe original hollow filaments that it was understood the orientation wasnot disturbed by drawing but orientation was rather improved.

EXAMPLE 2

Poly(methyl methacrylate) series optical filaments (filament diameter250 μm) as the original sheath-core type filaments were drawn at asupplying speed of 0.3 m/min by the similar means to Example 1. It wasconducted with a power density of 23.9 W/cm². In this case, the drawnfilaments with a filament diameter of 14 μm (draw ratio 319 times) at awinding speed of 139.8 m/min, the filament diameter of 12 μm (draw ratio433 times) at a winding speed of 226.2 m/min and the filament diameterof 7 μm (draw ratio 1274 times) at a winding speed of 400 m/min wereobtained. When the drawing tension corresponds to each of these drawingratios were measured by the load cell according to the method shown inFIG. 1, they were 0.12 MPa at a filament diameter of 14 μm, 0.18 MPa atthe filament diameter of 12 μm and 0.25 MPa at a filament diameter of 7μm. Still, drawing of the high drawing ratio of 100 times or more wasnot possible under the tension of more than 10 MPa. Also, the drawing ofthe high ratio was not possible even with the low drawing tension ofless than 0.001 MPa.

6. INDUSTRIAL APPLICABILITY

By making the sheath-core type super microfilaments by the simple andconvenient drawing means from the sheath-core type filaments such as thehollow filaments, the optical filaments and the conjugate filaments, thenon-woven fabrics and the like consisting of good thermal retainingclothes, super micro optical fibers and conjugate filaments can bemanufactured.

1. A method of manufacturing drawn sheath-core type filaments which comprises providing an applied tension of 10 MPa or less and heating with infrared beams irradiated from at least two directions, and then drawing original sheath-core type filaments at a drawing ratio of 100 times or more.
 2. A method of manufacturing drawn sheath-core type filaments according to claim 1, wherein said tension is provided by the own weight of the original sheath-core type filaments.
 3. A method of manufacturing drawn sheath-core type filaments according to claim 1, wherein said infrared beams are irradiated within up-and-down 4 mm of axial directions of the filaments at the center of the original sheath-core filaments.
 4. A method of manufacturing drawn sheath-core type filaments according to claim 1, wherein said infrared beam is a laser beam.
 5. A method of manufacturing drawn sheath-core type filaments according to claim 1, wherein said original sheath-core type filaments are delivered by a blowing duct and guided to said infrared beams.
 6. A method of manufacturing drawn sheath-core type filaments according to claim 1, wherein a guiding tool for controlling the position of the original sheath-core type filaments is disposed before said original sheath core-type filaments are heated by infrared beams.
 7. A method of manufacturing drawn sheath-core type filaments according to claim 1, wherein the drawn sheath-core type filaments connected to the original sheath-core type filaments are obtained by stopping the infrared beam irradiation in said drawing process and taking out a product in a state that the original sheath-core filaments are connected to the drawn sheath-core filaments.
 8. A method of manufacturing drawn sheath-core type filaments according to claim 1, wherein said drawn sheath-core type filaments are heat treated by a heating zone disposed subsequently.
 9. A method of manufacturing drawn sheath-core type filaments according to claim 1, wherein said drawn sheath-core type filaments are further drawn.
 10. A method of manufacturing: drawn sheath-core type filaments according to claim 1, wherein plural numbers of said sheath-core type filaments are further drawn reeling off at the same time and wound-up in a unified manner.
 11. A method of manufacturing non-woven fabrics comprised of drawn sheath-core type filaments according to claim 1, wherein said drawn sheath-core type filaments are accumulated on a running conveyor.
 12. A drawing starting method of drawn sheath-core type filaments according to claim 1, wherein said original filaments are drawn by the tension provided by the own weight and drawn thereafter by predefined wind-up speed in the manufacturing method of said drawn sheath-core type filaments.
 13. An apparatus for manufacturing the drawn sheath-core filaments comprising a supply device for the original filaments consisting of sheath-core type filaments, an infrared ray heating device composed of heating within up-and-down 4 mm in the axial direction of the original filaments at the center of the original filaments by irradiating infrared beams from plural directions and having means for controlling to draw at 100 times or more the heated original filaments by providing a tension of 10 MPa or less.
 14. An apparatus for manufacturing drawn sheath-core type filaments according to claim 13, wherein said infrared beam is a laser beam radiated from a laser emitter.
 15. An apparatus for manufacturing drawn sheath-core type filaments according to claim 13, wherein a radiation means from plural directions of said infrared beams are reflection using mirrors of the irradiated beam from one direction.
 16. An apparatus for manufacturing drawn sheath-core type filaments according to claim 13, wherein a radiation means from plural directions of said infrared beams are the beams from plural infrared beam emitters.
 17. An apparatus for manufacturing drawn sheath-core type filaments according to claim 14, wherein said laser beam is a carbon dioxide gas laser having a power density of 10 W/cm² or more.
 18. An apparatus for manufacturing drawn sheath-core type filaments according to claim 13, wherein a guiding tool controlling the position of the original sheath-core filaments is disposed before said original sheath-core type filaments are heated by said infrared beams.
 19. An apparatus for manufacturing drawn sheath-core type filaments according to claim 18, wherein said guiding tool has a position control device which can finely adjust the guiding position of said original sheath core type filaments.
 20. An apparatus for manufacturing drawn sheath-core type filaments according to claim 13, wherein it is composed that a blowing duct is disposed before said original sheath-core type filaments are heated by said infrared beams and the original sheath-core type filaments are delivered by the blowing duct.
 21. A drawn sheath-core type super microfilament according to claim 1, wherein said drawn sheath-core type filaments consist of sheath only, and are hollow filaments of which insides are gas and outside diameters of the drawn sheath-core type filaments are 10 μm or less.
 22. A drawn sheath-core type super microfilament according to claim 1, wherein said drawn sheath-core type filaments are hollow filaments for dividual fibers and have many cracks in longitudinal directions of the drawn hollow filaments.
 23. A drawn sheath-core type super microfilament according to clam 1, wherein said drawn sheath-core type filaments are micro-porous-film hollow filaments having many micro-pores on walls of the drawn filaments.
 24. A drawn sheath-core type super microfilament according to claim 1, wherein said drawn sheath-core type filaments consist of polymers which have a light transmittance of 85% or more for the core components, and are optical filaments with the filament diameters of 30 μm or less.
 25. A drawn sheath-core type super “microfilament according to claim 1, wherein the core components of said drawn sheath-core type filaments are silica series glass or fluoride glass, and are the optical filaments with filament diameters of 10 μm or less.
 26. A drawn sheath-core type super microfilament according to claim 1, wherein said sheath-core type filaments are conjugate filaments and the sheath components of the conjugate filaments consist of adhesive polymers.
 27. A sheath-core type filament according to claim 7, wherein said original sheath-core type filaments and said drawn sheath-core type filaments are connected optical filaments.
 28. A sheath-core type filament according to claim 7, wherein said original sheath-core type filaments and said drawn sheath-core type filaments are connected hollow filaments. 